Predicting device



. April 15, 1930. T. .1. STEPHENS PREDICTING DEVICE Filed Dec. 1926 3mm Thomas J- Stephens Patented Apr. 15, 1930 UNITED STATES PATENT QFFICE THOMAS J'. STEPHENS, OF THE UNITED STATES ARMY, FORT MONROE, VIRGINIA PREDIGTING- DEVICE Application filed December 7, 1926. Serial No. 153,185.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 30, 1928 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The subject of this invention is a predicting device.

In plotting the prediction or set forward point of a moving target the present gunnery practice is to plot the course of the target 10 on a map by marking the position of the target at stated intervals. In order to calculate the predicted future position of the target the time of flight of the projectile must be taken into consideration. The instrument commonly used to establish this point is a slide rule the operation of which necessitates the setting of values thereon and includes a mental calculation.

With a view to reducing the personal equation to a minimum the present invention contemplates a plotting device which having but a single scale may be set during the interval between plotting observations, reduces the possibility of error, provides greater flexibility and allows easier and more rapid operation.

With the foregoing and other objects in view, my invention resides in the novel arrangement and combination of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.

A practical embodiment of the invention is illustrated in the accompanying drawings, wherein:

Fig. 1 is a plan view of a predicting device constructed in accordance with the invention;

Fig. 2 is a view in rear elevation thereof;

Fig. 3 is a detailed sectional view on the line 3-3 of Fig. 1;

Fig. 4: is a sectional view on the line H of Fig. 1;

Figs. 5, 6 and 7, are respectively plan, side and rear elevational views of the carrier.

Referring to the drawings by numerals of reference:

The device comprises a base plate A to which is attached a guide B which is normal to the reading edge XY of the plate. Mounted on the guide B is a movable carrier G on which is a fixed arm D and a pivoted arm E whose fiducial edges intersect at a point F which is always on the normal to the reading edge X-Y through a zero reference P corresponding as will be seen later to the present position of the target. That this condition may be true irrespective of the angular displacement of the movable arm, the pivot of said arm coincides with the point F. In order that the arm E may be rotated to vary the angle made by its fiducial edge with the normal through P it is secured to or provided with a worm segment 6 which is engaged by a worm G mounted in a housing H secured to the carrier and including a handle portion J by means of which the complete device may be conveniently moved about over a map.

The pivot arm E is formed with an arcuate extension K on which is a scale L graduated in values of time of flight or range as a function of the position of the target. The pointer M against which this scale is read is fixed to the carrier C. The pivot arm E also carries a slide N having a depending casing 71 in which is mounted a spring held marker R which preferably assumes the form of a pin so that when the slide is moved until the casing it strikes the raised edge of the base plate, the marker may be pressed to indicate on the underlying map a point which is in line with the edge PY of the base plate. The center of the marker R therefore constitutes the effective reading edge of the arm E.

The scale L is graduated so that for any setting the following relation will be true:

Tang. anzle made by arm E with normal through P: Tang. angle made by arm D with normal through P Predicting interval plus time of flight or range Observing interval Therefore when the arm M registers zero time of flight the arms E and D will make the same angle with the normal through P.

The operation of the devicejs as follows: When the course of the target has been plotted on the map the device is placed on the map with its edge PY lined up with the indicated course, zero P being placed on the last plotted point on the map which represents the present position of the target. The carrier C is then moved until the fixed arm D intersects the edge PY of the base plate at the next to the last plotted point on the map. The pivot arm E carrying the scale L is then rotated until the value of the time of flight to the present position of the target, to which may be added correction factors, registers with the pointer M. The value of time of flight is derived in the accustomed manner from a table of ranges and the range from gun to target may be determined by means of a telemeter or directly measured from the map. The slide N on the pivot arm is then moved until its casing strikes the edge of the base plate and the marker R when pressed indicates the predicted or set forward point on the map from which point the firingdata may be taken.

In actual practice the pivot arm is moved to its final position to set the time of flight scale during the interval between the final plotting operations and in this way the total dead time of maneuver is reduced promoting greater accuracy and rapidity in firing.

I claim 1. A predicting device embodying a base plate having a fixed zeroon its reading edge corresponding to present position of a target, a carrier movable on the base plate normal to the reading edge through the zero point, a fixed and a pivoted arm on the carrier intersecting the reading edge of the plate and respectively establishing a constant angle and a varying angle with the normal through the zero point, an arcuate extension on the pivoted arm having a graduated scale interpreting values of a function of the present position of the target, a pointer on the carrier against which said scale is read, a slidable marker on the pivoted arm and means for rotating said arm.

2. A predicting device embodying a base plate having a fixed zero on its reading edge corresponding to present position of a target, a carrier movable on the base plate normal to the reading edge through the zero point, a fixed and a pivoted arm on the carrier intersecting the reading edge of the plate and respectively establishing a constant angle and a varying angle with the normal through the zero point, means for rotating the pivoted arm, means interpreted in values of a function of the present position of the target for affording a measure of the angularity tobe imparted to the pivoted arm and means on said arm for indicating the predicted future position of the target.

3. A predicting device embodying a base plate having a fixed zero on its reading edge corresponding to the present position of a target, a carrier movable on the base plate norreal to the reading edge through the zero point, a fixed and a pivoted arm on the carrier intersecting the reading edge of the plate and respectively establishing a constant angle and a varying angle with the normal through the zero point, means for rotating the pivoted arm, and means interpreted in values of a function of the present position of the target for affording a measure of the angularity necessary to be imparted to the pivot arm to have it intersect the reading edge of the base plate at the predicted future position of the target.

4. A predicting device embodying a base plate having a fixed zero on its reading edge, a pivot arm for establishing varying angles with the normal through the zero point, means interpreted in values of a function of present position of the target for affording a measure of the angularity to be imparted to said arm and means for establishing by reference to a plotted course the position of the pivotal point of said arm on the normal through the zero point.

A predicting device embodying a base:

plate having a fixed zero on its reading edge, an arm for establishing a constant angle with the normal through the zero point, said arm movable along the normal to intersect the reading edge of the base plate and lay off the travel of a target through an observed interval and means associated with said arm and set according to the value of a function of the present position of the target for laying off on the reading edge of the plate the predicted future position of the target.

THOMAS J. STEPHENS. 

